Washing tow bundles of synthetic fibers



Aug. 16, 1960 c. F. oLDERsHAw 2,949,337

WASHING Tow BUNDLES oF SYNTHETIC FIBENS Filed June\24, 1957 United States WASHING TOW BUNDLES OF SYNTHETIC FIBERS Charles F.'0ldershaW,-Concord, Calif., assigner to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed June y214, 1957, Ser.` No. 667,655

'14 Claims. (Cl. 8-151.2)

In the manufacture of many of the so-called artiiicial Silks and other man-made synthetic textile ber commodities from various ber-forming materials, it is oftentimes required to wash out or extract various impure substances and undesired constituents from the freshly spun filamentary products in order to provide them in a satisfactorily useful and commercially acceptable form. Wet spun yarns and iilaments, for example, must generally be washed in a suitable extractant medium or washing liquid (that frequently may be water or an aqueous liquid) in order to remove residual quantities of the spinning solution solvent that was employed to obtain the fiber-forming material in extrudable form, as well as any coagulant that may persist in the freshly spun ber by entrapment or entrainment after its withdrawal from `the coagulating spin bath. Of course, the washing liqquid must be one that is miscible with and have unsatisiied capacity for the spinning solution solvent or any other impurities, or both, that are being removed. Certain of the artificial and synthetic textile fibers that are prepared by dry or evaporative spinning techniques may also require washing for similar purposes subsequent to their extrusion. Likewise, some of the melt spun synthetic filamentary materials may need to be washed after being spun. Thus, by way of illustration, certain of the superpolyamideiibers, particularly those that are derived from epsilon-caprolactam (which are sometimes popularly known as being nylon 6type materials), must usually be Washed after spinning in order to be rid of intolerably high contents of monomer and undesirably low molecular weight polymer that invariably obtains in the freshly extruded material.

For purposes of washing and otherwise processing many synthetic and artificial textile fiber materials subsequent to spinning, it is usually convenient and expedient to form the fibers in continuous or endless filamentary lengths that, during or subsequent to spinning, are assembled in multiple filament tow bundle arrays or gathered arrangements in which a plurality of individual, component continuous filaments are handled in a closely associated, substantially or ostensibly parallel relationship. This is particularly the case for many of the wet spun synthetic textile materials including those that are derived from fiber-forming acrylonitrile polymer compositions, particularly polyacrylonitrile and other fiberforming copolymers that contain in the polymer molecule at least 80 percent by Weight of acrylonitrile.

The main purpose and chief concern of the present invention is to provide an improved process and highly advantageous apparatus for use in conjunction therewith for washing or leaching undesired extractable constituents or impure substances, or both, from the various articial and synthetic textile fiber materials during their processing in the form of multiple continuous filament tow bundles subsequent to spinning. It is a particular objectan'd specific regard of the inventionto deal with the lWashing of wet spun synthetic textile materials,

2,949,337 Patented Aug. '16, 1960 especially iibers from acrylonitrile polymer compositions that are obtained in an aquagel form upon their spinning and during their immediately subsequent processing 4and handling prior to drying, such as the `water-swollen or hydrated iilamentary structures that may be derived by Wet-spinning extrudable solutions -of acrylonitrile polymers in polyacrylonitrile-dissolving aqueous saline solvents, particularly zinc chloride and its saline-equivalents for such purpose, into aqueous, non-polymer-dissolving coagulating spin bath solutions of the samesaltor salts. And, as can readily be comprehended by `those-who are skilled in their calling, the broader aspects of the -present invention include an improved process and apparatus for any liquid treatment upon -any iilamentary 'material, including those ofnatural origin, wherein -itmay be `desired to handle the filaments in ya-tow-like gathering (such as in silver or roving-resembling arrangements) for passage through a bath of any desired treating liquid which may be beneiicial to the fibers (suclras bleach liquids, dyebaths,scouring solutions, iinish andlubricantapplicating compositions and the like) wherein the liquid is caused to flow-such that its general andoverall mannerof progression through the'bath is either concurspinning solution Vsolvent or other impurities, or "both,

from the freshly'wet or otherwise spun filaments, whereinthe liquid in said bath'is being moved througha-plurality of at least two intercommunicating' stages (of'which said bath is comprised) in a Vgenerally concurrent or countercurrent direction with or against the direction of travel of said Vtow btmdlethrough said bath, and, in each of'said stages, divertingaportion of the treating -liquid that is contained therein forforced passage through and between the individual iilaments or bers in'said tow Ybundle in a direction that is countercurre'nt tothe passage of said tow bundle throughsaid bath and divertingth'e balance of the treating liquid'for Vforced passage `through and between the individual filaments or iibers in said tow bundle in a direction that is concurrent with the passage of said tow bundle, said diverted portions in `all but the iirst and last stages of said bath being directed to the next adjacent stages that are in bidirectional sequence with the'stage from which it isbeing diverted.

Advantageously, the liquid in said treating bath is passed in a generally overall countercurrent manner of flow against lthe tow bundle being passed in non-interrupted vsubmersioin through the sequential bath stages and the liquid'that is contained in and diverted from each stage excepting the first and last is obtained from the next adjacent upstream stage (with respect to'the flow Yof treating liquid through said bath), said treating liquid being admitted to said bath in or through the last of said stages and being withdrawn ifrom said bath after having 'ultimately passed therethrough from the first of said stages. nMore advantageously, each of said stagesris comprised (or may conveniently be considered to be comprised) of an open, liquid-containing section and 'a corined, liquidcontaining, chamber section, each of which are contiguous and in communication with one another and with opposite type liquid-containing means in each of the next adjacent stages, said liquid in each stage being diverted from said confined chamber therein downstream countercurrent through said tow bundle into said open section in the same stage and upstream concurrent with said tow bundle into the open section of the next adjacent upstream stage, said liquid in each confining chamber of each stage being obtained and circulated from the open section of the next adjacent upstream stage.

Apparatus that is in accordance with the invention is comprised of physical means for handling the tow bundle and the beneficial treating liquid therefor in the same multiple stage bath in the 4-above indicated manner.

The invention is further delineated and manifest, in both process and apparatus embodiments that are not intended to be limiting thereof, in the following description and specification, taken in connection with the accompanying drawing, wherein:

Figure 1 is a plan view of an apparatus adapted to accomplish the practice of the present invention which is illustrated in a fragmentary manner;

Figure 2 is a side elevation in cross section of an apparatus similar to that depicted in Figure l as might be seen along the line 2 2 therein with certain of the features drawn in phantom outline and showing, in `addition thereto, a bath of beneficial treating liquid in the apparatus and a tow bundle being passed therethrough for treating according to the present process; and

Figures 3 and 4 are elevations in section taken along the lines 3-3 and 4 4 in Figure l, respectively.

With initial reference to the first ligure of the drawing, there is shown an apparatus that is adapted for utilization in the liquid treatment of textile liber tow bundles and the like by the process of the invention. The apparatus consists of a at, relatively shallow elongate pan or trough 5 for containing a desired bath of any beneficial treating liquid (not shown in Figure 1). The trough 5 is divided or separated `along its ylength into a plurality of adjacent, intercommunicating, liquid treating units or stages that are sequentially designated bythe letters A, B, M, N and Z and which are separated, for clarity, by the dotted lines that are interspersed therebetween. A final extra stage X is provided at the end of the bath (and is yalso an integral part thereof) to facilitate the admission of liquid to the bath and the withdrawal of the treated tow bundle therefrom. Although it is usually convenient `and preferred to add all or substantially all of the continuous fresh supply of treating liquid at one end of the bath, it is quite apparent that portions of the total treating liquid can be added at one or more of the intermediate stages. The same goes for withdrawal of the spent or used (or partially spent) liquid from the bath.

As has been indicated, any desired plurality of stages may be employed, depending upon the particular liquid treatment being effected and the conditions under which it is being performed as well as the efficacy, degree or extent of treatment that is desired to be achieved. In general, for purposes of washing freshly spun tow bundles, it is usually `advantageous to employ at least six and frequently more advantageous to utilize eight or more separate stages in a bath designed for accomplishment of any conventional treatment.

Each of the stages A, B, M, N, and Z is comprised of contiguous open, liquid-containing sections, designated A1, B1, M1, N1 land Z1, respectively, and enclosed, liquidconfining sections or chambers, design-ated AZ, B2, M2, N2 and Z2, respectively. The open sections 'are alternately disposed in each stage towards the tow-introducing end of the trough 5 in the direction of the roller guide 6, which is adapted to be submerged in the bath of treating liquid and to pass the tow bundle into immersion therein upon its introduction to the bath. Each of the open sections is in communication with the contiguous confined section in the same stage through a tow and liquid passing aperture, designated 7, 8, 9, and 11 in each of the stages A through Z, respectively. Each of the confined liquid-coniining sections is in tow passing and liquid diverting communication with the immediately adjoining open section in the next 'adjacent stage through an aperture, designated 12, 13, 14, and 15 in each of the stages A, B, M and N. The aperture 12 for example, 4that connects confined section A2 with open section B1 is shown in elevation in Figure 3. The aperture 8 between sections B1 and B2 can be seen in Figure 4. In the last stage Z, the liquid confining section Z2 is in communication with the extra stage X through the aperture 16.

As is implied earlier in the foregoing, the wash unit or stage designation that is employed herein is arbitrarily based on convenience and for purposes of preferred delineation. If desired, yand possibly in better keeping with certain viewpoints that may be maintained in the art of extractive processes, each of the stages could well be considered as spanning or extending between the points of countercurrent liquid ow from each of the enclosed chambers directly to each adjacent open section. According to such concept, for example, the chamber M2 and the open section N1 would comprise a single stage as would the chamber N2 and open section Z1, and so forth. In either event, as can readily be appreciated, both the process and apparatus of the present invention would function and be embodied in the same Way with only the indicated difference in definition being lat variance.

Reverting to the descriptive scheme herein adhered to, a conduit connects leach of the open sections excepting for the first with the immediately adjacent confined section in the adjoining stage towards the tow-introducing end of the trough 5. Thus, confined section A2 is connected with open section B1 through the conduit 17; M2 with N1 through conduit 21; and N2 with Z1 through conduit 23. The confining section Z2 in the last stage is connected with the extra stage X with condfuit 2S. Each of the conduits 17, 19, 21 and 23 is adapted to withdraw liquid from 'an upstream, open, liquid-containing section (with respect to the flow of a countercurrently moving liquid) and pass it into the immediately adjacent downstream section in a generally countercurrent manner of transmission through the bath for dual simultaneous diversion from each of the confining sections with and against the tow bundle (also shown in `Figure l) passing through each of the stages in the bath. The conduit 25 that connects the extra sta-ge X with the confining section Z2 of the last stage Z admits the freshly introduced treating liquid for generally countercurrent ow progression through the sequential stages of the bath.

As is apparent, the extra stage- X may be dispensed with if it is desired to directly admit the fresh liquid to the confining section Z2 of the last stage and to withdraw the treated tow bundle, without purposive concurrent diversion of treating liquid, from the confining section of the last stage through suitable liquid sealing means that may be provided therein. Usually, however, it is more convenient and of obvious advantage to provide an extra open, liquid-containing stage beyond the last confining section in the sequential stages (as is depicted) to facilitate meeting both liquid and tow-handling requirements. It is usually suitable, in such instances, to concurrently divert treating liquid from the last confining section inthe stages to such extra stage with the tow bundle passing through the bath.

From the foregoing, it is apparent, and as is shown in Figure 2 of the drawing, that treating liquid is circulated i-n a generally countercurrent manner through the bath L by being admitted to the extra stage X in the bath, passed therefrom to the confining section Z7. in the last stage; partially forwarded or diverted countercurrent to the tow bundle T through and between the individual filaments or fibers thereof through the aperture 11 into the open section Z1 of the last stage; passed therefrom to the confining section N2 i-n the next adjacent downstream stage N, and so forth until it has been linally transmitted to the open section A1 in the first Stage of the bath from which it is withdrawn as spent or used treating liquid through the outlet conduit 27. Pump means `18, 20, 22, 24 and 26 inor with each of the conduits 17, y19, 21, 23 and 25, respectively, may Iadvantageously be employed to accomplish the generally countercurrent liquid forwarding action. During the countercurrent flow of the treating liquid through the stages in the bath, a portion of the liquid that is being circulated through each stage isdiverted. or recycled concurrent with the fiber from each ofthe confined sections A2, B2, M2, andv N2 into the immediately adjacent upstream open section- (B1, M1, N1 and Z1, respectively) through the apertures 412, 13, 14 and 15, respectively, in `the confined sectionsl of eadh of the sequential stages. As has been mentioned, a portion of the liquid in the confined section Z2 of the last stage may be recycled into the extra stage X, if so desired.

The relative liquid forwarding Iand recycle rate that is effected with the diverted liquid from the confined sections in the stages throughout the bath is generally best when it is about the same in each stage. Of course, it may vary in specific instances with the particular liquid treatment that is being effected. It is ordinarily desirable for the countercurrent forwarding rate of the liquid from each of the confined sections to each of the open sections in each stage to be sufficient to effect an optimum concentration of extracted impurities at the exit of each chamber and to secure all the desired ushing action through and between -the filaments or fibers in the tow during their passage through the intercommunicating aperture. Thus, las can be seen, a balance must be struck in specific instances between the volume of liquid that is desired to be handled and the efficacy of treatment considered suitable, taking into account (especially in extractive processes) that larger quantities of treating liquid frequently assure a more thorough and complete treatment. The countercurrent forwarding rate, as will be apparent, does not particularly depend upon the relative speed with which the tow bundle is being passed through the bath or upon its size or the number of filaments that it contains. Rather than any of these, the net countercurrent forwarding rate is approximately fixed and equal to the quantity of treating liquid being ladmitted to the bath per unit time, regardless of the quantity of tow being treated therewitlh.

It is usually `desirable for the tow-accommodating size of the apertures that provide passage for the tow and liquid between the sequential stages in the bath to be shaped to fit fairly Iabout the tow, regardless of the particular configuration in which the tow bfundle is being handled. It is usually satisfactory, incidentally, to employ generally round tow bundles and to provide round matching apertures for its pass-age through the stages, although relatively fiat, ribbon-like tow bundles and the like arrays (or -tows having other desired configurations) can also be handled through appropriately formed apertures. A relatively close-clearing aperture for the tow handle permits an extremely effective flushing and washing action of the treating liquid on the filaments or fibers in the tow to be achieved during the passage of the tow through the interconnecting apertures, particularly of tfhe liquid being forwarded countercurrently against the tow. In this connection, it is usually desirable (though not an absolute necessity) to employ tow bundles that are of considenable magnitude in the practice of the invention, such as those that may be comprised of in the neighborhood of 3,000 and oftentimes many more individual gathered filaments or fibers.

When freshly spun fibers are being washed, it is usually advantageous for the proportion of diverted wash liquid in each stage that is forwarded countercurrent against the tow and recycled with the tow to be in a ratio of not more than one partby volume of forwarded liquid to each 5 parts by volume of recycled liquid. More adanvtageously, this proportion of diverted wash liquid that is countercurrently forwarded is in a ratio of the indicated variety that is not greater than one to 20. Preferably, the ratio is not more than one part by volume of forwarding liquid for each 30- parts by volume of recycle, especially when freshly wet spun acrylonitrile polymer aquagel lilaments 'are bei-ng washed in an aqueous liquid.

The natio of forwarding and recycling liquid in each stage can be set and adjusted in various ways to divert the desired proportionsV of liquid countercurrent against and concurrent with the tow from each of the confined sections. The simplest manner, as is apparent, is to accompi-lsh'the desired proportioning by using the forwarding and recycling apertures leading out of the confined spaces 'as kpressure-dropping orifices of different effect and consequence in each stage to facilitate realization of the desired diverse, oppositely-directed rates of flow of the separate liquid streams being diverted from each confined section. The cross-sectional area or diameter of the apertures can be varied to accomplish this effect, with given sized tow bundles and given liquid supply pressures to each of the confining sections.

More advantageously, pressure dropping orifice tubes of suitable length iandcross-sectional proportions (benefcially with the concurrent tubes having a slightly larger cross-sectional area than the countercurrent tubes at each oppositely `liowing point of liquid diversion) may be employed for the purpose. Thus, longer and shortertubes having respectively greater and lesser pressuredropping effects may be utilized to proportion the flow of forwarding and recycling liquid in each stage in a manner that will be apparent to those skilled in the art. The longer the tube and the greater the pressure drop it achieves, the less will be the flow through the aperture in which such tube is provided.

The tube orifice members 30, 31, 32, 33 and 34v in the apertures 7, 8, 9, 10 and 11, respectively, which accommodate the countercurrent forwarding ow of liquid from the confining sections A2, B2, M2, N2 and Z2, respectively, in the stages A, B, M, N and Z, respectively, as is shown in the drawing, may be made longer than the tube orifice members 35, 36, 37, 38 and 39 in the same sections that control the concurrent recycling flow of the treating liquid in order to effect a relatively greater rate of liquid recycling than forwarding in and from each of the stages. As can be appreciated, the relative rates of forwarding and recycling, especially with close to the same diameter orifice tubes, are generally proportional to the length of the tubes employed, taking into account the llow retarding and assisting action of the tow passing against or with the liquid through the various tubes involved. When properly proportioned and sized tubes are employed, an excellent control of relative liquid forwarding and recycle flow rates can be attained in each stage. Furthermore, the employment of tubes greatly facilitates the realization of an optimum manner of the flushing action that is involved during the liquid treatment, especially in the countercurrent passage of liquid through the tow bundle, due to the pronounced flaring effect thereby caused in the tow.

If desired, incidentally, the confined sections can be provided with removable covers and the tubes (and enclosing wall portions of the conned sections) furnished with closeable slot arrangements to facilitate lacing-up of the tow bundle in and through the stages in the bath.

An Aadditional feature of great advantage in apparatus according to the invention is the provision of liquid level maintaining spillways or wiers in each of the open sections of the stages about each of the points of liquid withdrawal therefrom. These are depicted in the drawing as the box-like spillway partition structures 40, 41', 4-2, 43, 44 and 45 in each of the open sections of the stages A, B, M, N, Z and in the extra stage X, respectively. Such partitions, or means equivalent thereto, effectively control the liquid level in the bath at a desired height (or depth of liquid) and facilitate achievement of the desired manner of iiuid handling during the process. They also permit larger conduits to be employed for transfer of the liquid from stage to stage without didiculties due to possible overliow or overwithdrawal and advantageously permit pumping means to be employed that have iloat valve controls so as to be quickly responsive to changes in operating conditions.

To further illustrate the invention, an apparatus similar to that shown was employed to wash a round tow bundle of about 3000 individual continuous laments of freshly wet spun polyacrylonitrile aquagel iibers that had an ultimate individual ber size, when finally dried and converted to finished form, of about 3 denier each and which, upon withdrawal from the coagulating spin bath in aquagel form prior to washing, contained about 9 parts by weight of a 43 percent by Weight aqueous zinc chloride solution for each part by weight of polymer, on a dry weight basis, in the tow bundle. The wash bath had a total length of about 9 feet and a width of about 6 inches. It contained aqueous wash liquid at a depth of about 21/2 inches. It was divided into eight stages. Each stage, excepting for the irst stage and the extra stage in the bath had a length of about l inches, about 1/3 of which in each stage was the confined chamber section with a height in each chamber about equal to the depth of the bath. Each of the apertures for diverting liquid Afrom the confined sections had effective outlet diameters of about 1/z inch and were in the form of pressure-dropping tube orifices; the countercurrently forwarding tubes having lengths of about 5 inches and the concurrently recycling tubes about 11A inches. The tow bundle was passed through the bath at a linear rate ot about six feet per minute. Fresh water was admitted to the extra stage at about 200 cubic centimeters per minute. The liquid was circulated through the bath with a forwarding rate in each stage countercurrent to the tow bundle of about 200 cubic centimeters per minute and a recycle rate in each stage of about 6,000 cubic centimeters per minute. The spent aqueous wash liquid that was withdrawn from the first stage contained about 35 percent by weight of dissolved zinc chloride that was extracted from the aquagel. The washed tow bundle, upon withdrawal from the extra stage, contained about 4 parts by weight of water per part of polymer and less than 0.05 percent by weight of zinc chloride, based on the weight of the fiber. Upon subsequent drying, the aquagel was converted into excellent quality, tine denier polyacrylonitrile textile fibers.

Analogous good results can be obtained when the present invention is practiced to wash other freshly spun artificial and synthetic fibers and for the accomplishment of other desired liquid treatments on ltow bundles and the like arrays of various textile filaments and bers using baths of either generally concurrent, but preferably countercurrent, treating liquids. As will readily occur to those having an interest in the present invention, generally concurrent flowing baths are provided and handled in a manner that is approximately the reverse or opposite of that which has been described.

Since many changes and modiiications in the practice of the invention can be made without substantially departing from its intended spirit and scope, it is to be understood that the invention is to be construed and interpreted as it is set forth and dened in the hereto appended claims.

What is claimed is:

1. Process for treating textile iibers in tow bundle and the like form with beneficial treating liquids which cornprises passing said tow bundle through a circulating bath of said liquid that is separated into a plurality of at least two individual stages which are in tow bundle-passing and liquid flowing communication with one another; and, in

each of said stages, diverting a portion of the treating liquid that is contained therein for forced passage through and between said tow bundle in a direction that is countercurrent thereto and diverting the balance of said liquid for forced passage through and between said tow bundle in a direction that is concurrent therewith.

2. Process for treating textile fibers in tow bundle and the like form with beneficial treating liquids which comprises passing said tow bundle through a bath of said liquid circulating said bath in a generally countercurrent flow to the tow bundle in the bath, said bath consisting of at least two separate, intercommuncating stages, the liquid in each of said stages being partially contained in an open condition nearest to the tow-introducing end of said bath and partially contained in a contiguous, confined condition; said tow bundle being passed through each portion of said liquid portions in each of said stages; passing fresh treating liquid through the last of said stages furthest from the tow-introducing end of said bath and circulating it through each of said stages in such a manner that a portion of the liquid is forwarded countercurrently from said coniined portion of liquid in each stage through and between said tow bundle passing therethrough and the balance of said liquid is recycled concurrently from said coniined portion of liquid in each stage to the open portion of liquid in the adjacent upstream stage with said tow bundle passing therethrough; said liquid being passed downstream in said bath from the open portion of liquid in each stage to the confined portion of liquid in the next adjacent downstream stage.

3. The process of claim 2, wherein said bath is divided into at least eight stages.

4. The process of claim 2, wherein a greater proportion of said liquid being circulated through said bath is diverted concurrent with said tow bundle from each stage than countercurrent against it therein.

5. The process of claim 4, wherein the tow bundle consists of freshly wet spun continuous filament acrylonitrile polymer aquagel bers and said liquid is an aqueous washing liquid therefor.

6. The process of claim 5, wherein said bath is divided into at least eight stages and at least 20 parts by volume of said aqueous wash liquid is diverted concurrent with said tow bundle from each stage for each part by volume that is diverted countercurrent against said tow bundle therein.

7. Apparatus of the character described and for the purposes indicated comprising a pan for containing an elongate bath of beneficial treating liquid for textile fibers; structural means in said pan dividing said bath into a plurality of intercomunicating stages; tow-advancing means for longitudinally passing a tow bundle of textile fibers through said bath and each of the stages therein; means defining an aperture in the structure of each of said stages for diverting liquid in each stage in forced passage through and between a tow bundle passing through said aperture in directions both concurrent with and countercurrent to said tow bundle passing therethrough; and pump means for circulating treating liquid longitudinally through said bath in a general path of flow relative to the direction of the tow bundle when it is passed therethrough.

8. Apparatus of the character described and for the purposes indicated comprising a pan for containing an elongate bath of beneiicial treating liquid for textile fibers; structural means in said pan dividing said bath into a plurality of intercommunicating stages, said structural means forming in each of said stages an open, liquid-containing section and a conned, liquid-containing section therein in communication with one another and in the same sequence in each of the stages in said bath, said open and confined sections of sequential alternate stages being in communication with one another; tow-advancing means for longitudinally passing a tow of textile bers through said bath and each of the alternate sec- 9 tions of each of said sequential stages; means defining an aperture in the structure of each of said confined sections in each of said stages for diverting liquid in each stage in forced passage through and between a tow bundle passing through said aperture in directions both concurrent with and countercurrent to said tow bundle passing Itherethrough; pump means for admitting and circulating treating liquid longitudinally through said bath in a general path of flow relative to the direction of the tow bundle when it is passed therethrough; and conduit means for passing liquid from each of said open sections in each of said stages excepting the first to the adjacent confined section in each sequential stage in the saine path as the general direction of circulation of said liquid in said bath.

9. Apparatus of the character described and for the purposes indicated comprising a pan for containing an elongate bath of beneficial treating liquid for textile fibers; towadvancing means for longitudinally passing a tow bundle of textile fibers in and through said bath; pump means for admitting fresh -treating liquid at one end of said bath and circulating it therethrough in a path of flow generally countercurrent to said tow bundle; a sequential spaced plurality of liquid-confining chambers formed in and physically dividing said pan with adjacent open sections therebetween and at the tow-introducing end of said bath, each of said chambers having a pair of apertures formed one in each of their sides that extend across said pan, each of said apertures in said chambers being in liquidtransmitting communication with the adjacent open sections of said bath-containing pan between said chambers and being further adapted to longitudinally accommodate and transmit said tow bundle in submersion in said bath when .it is being passed therethrough; a plurality of conduit means, each of said conduit means connecting an open section in said bath-containing pan toward the towintroducing end of said bath, each of said conduit means being adapted to pass liquid from each of said open sections to each of said chambers adjacent thereto in the same direction as the general path of circulation of said liquid through said bath; and a pump in each conduit for transmitting liquids in the indicated direction in each of said conduits.

l0. The apparatus of claim 9 and including, in combination therewith and in addition thereto, liquid fiow-restricting means for proportioning the rates of liquid flow `in opposite directions from each of the pair of apertures in each of said chambers to said adjacent open sections when a tow bundle is being passed through said bath and said bath-containing pan is full of bath liquid circulating therethrough.

11. Apparatus of the character described and for the purposes indicated comprising a pan for containing an elongate bath of beneficial treating liquid for textile fibers; tow-advancing means for longitudinally passing a tow bundle of textile bers in and through said bath; pump means for admitting fresh treating liquid at one end of said bath and circulating it therethrough in a path of flow generally countercurrent to said tow bundle; a sequential spaced plurality of liquid-confining chambers formed in and physically dividing said pan with adjacent open sections therebetween and at the tow-introducing end of said bath, each of said chambers having a pair of apertures formed one in each of their sides that extend across said pan, each of said apertures in said chambers being in liquid-transmitting communication with the adjacent open sections of said bath-containing pan between said chambers and being further adapted to longitudinally accommodate and transmit said tow bundle in submersion in said bath when it is being passed therethrough; tubular orifice members mounted in each of the pair of apertures in each of said chambers for proportioning the rates of liquid flow in opposite directions from each pair of apertures in each of said chambers to said adjacent open sections when a tow bundle is being passed through said bath and said bath-containing pan is full of bath liquid circulating therethrough, each of said tubular orilice members being adapted to fit closely about and longitudinally pass -a tow bundle therethrough; a plurality of conduit means, each of said conduit means connecting an open section in said bath-containing pan toward the tow-introducing end of said bath, each of said conduit means being adapted to pass liquid from each of said open sections to each of said chambers adjacent thereto in the same direction as the general path of circulation of said liquid through said bath; and a pump in each conduit for transmitting liquids in the indicated direction in each of sad conduits.

12. The apparatus of claim 1l, wherein the tubular orifice members in the apertures of each of said chambers on the side thereof that is in the direction of the towintroducing end of said bath are about equally longer than the equally shorter tubular orifice members in the apertures on the opposite sides of each of said chambers.

13. The apparatus of claim 9 and including, in combination therewith and in addition thereto, overow means in each of said open sections at the point of liquid withdrawal therefrom about each of said conduit means for maintaining the liquid level of said bath when it is contained in said bath-containing pan.

14. Apparatus of the character described and for the purposes indicated comprising a pan for containing an elongate bath of beneficial treating liquid for textile fibers; tow-advancing means for longitudinally passing a tow bundle of textile fibers in and through said bath; pump means for admitting fresh treating liquid at one end of said bath and circulating it therethrough in a path of fiow generally countercurrent to said tow bundle; a sequential spaced plurality of liquid-confining chambers formed in and physically dividing said pan with adjacent open sections therebetween and at the tow-:introducing end of said bath, each of said chambers having a pair of apertures formed one in each of their sides that extend across said pan, each of said apertures in said chambers being in liquid-transmitting communication with the adjacent open sections of said bath-containing pan between said chambers and being further adapted to longitudinally accommodate and transmit said tow bundle in submersion in said bath when it is being passed therethrough; a plurality of conduit means, each of said conduit means leading from one of said chambers into the bottom of the adjacent open section in said bath-containing pan toward the tow-introducing end of said bath, each of said conduit means being adapted to pass liquid from each of said open sections to each of said chambers adjacent thereto in the same direction as the general path of circulation of said liquid through said bath; a pump in each conduit for transmitting liquid in the indicated direction in each of said conduits; and a wier-like spillway at about the point of communication of each of said conduit means with each of said open sections for withdrawing liquid (firom each of said open sections into each of said conuits.

References Cited in the file of this patent UNITED STATES PATENTS 160,743 Barker Mar. 16, 1875 2,128,516 Graham Aug. 30, 1938 2,131,490 Nai Sept. 27, 1938 2,156,090 Hinnekens Apr. 25, 1939 2,558,734 Cresswell July 3, 1951 2,721,466 Nash Oct. 25, 1955 2,737,435 Borck Mar. 6, 1956 2,790,698 Robertson Apr. 30, 1957 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. '2,949,337 August l, 1960 Charles F. Oldershaw A It is hereby certified that error' appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l0, list of references cited, after line 69v insert the following:

Signed and sealed this 9th day of May 1961.

(SEAL) Attest:-

ERNEST We SWIDER DAVIDL Ii. LADD Attesting Officer Commissioner of Patents 

14. APPARATUS OF THE CHARACTER DESCRIBED AND FOR THE PURPOSES INDICATED COMPRISING A PAN FOR CONTAINING AN ELONGATE BATH OF BENEFICIAL TREATING LIQUID FOR TEXTILE FIBRES, TOW-ADVANCING MEANS FOR LONGITUDINALLY PASSING A TOW BUNDLE OF TEXTILE FIBERS IN AND THROUGH SAID BATH, PUMP MEANS FOR ADMITTING FRESH TREATING LIQUID AT ONE END OF SAID BATH AND CIRCULATING IT THERETHROUGH IN A PATH OF FLOW GENERALLY COUNTERCURRENT TO SAID TOW BUNDLE, A SEQUENTIAL SPACED PLURALITY OF LIQUID-CONFINING CHAMBERS FORMED IN AND PHYSICALLY DIVIDING SAID PAN WITH ADJACENT OPEN SECTIONS THEREBETWEEN AND AT THE TOW-INTRODUCING END OF SAID BATH, EACH OF SAID CHAMBERS HAVING A PAIR OF APERTURES FORMED ONE IN EACH OF THEIR SIDES THAT EXTENDS ACROSS SAID PAN, EACH OF SAID APERTURES IN SAID CHAMBERS BEING IN LIQUID-TRANSMITTING COMMUNICATION WITH THE ADJACENT OPEN SECTIONS OF SAID BATH-CONTAINING PAN BETWEEN SAID CHAMBERS AND BEING FURTHER ADAPTED TO LONGITUDINALLY ACCOMMODATE AND TRANSMIT SAID TOW BUNDLE IN SUBMERSION IN SAID BATH WHEN IT IS BEING PASSED THERETHROUGH, A PLURALITY OF CONDUIT MEANS, EACH OF SAID CONDUIT MEANS LEADING FROM ONE OF SAID CHAMBERS INTO THE BOTTOM OF THE ADJACENT OPEN SECTION IN SAID BATH-CONTAINING PAN TOWARD THE TOW-INTRODUCING END OF SAID BATH, EACH OF SAID CONDUIT MEANS BEING ADAPTED TO PASS LIQUID FROM EACH OF SAID OPEN SECTIONS TO EACH OF SAID CHAMBERS ADJACENT THERETO IN THE SAME DIRECTION AS THE GENERAL PATH OF CIRCULATION OF SAID LIQUID THROUGH SAID BATH, A PUMP IN EACH CONDUIT FOR TRANSMITTING LIQUID IN THE INDICATED DIRECTION IN EACH OF SAID CONDUITS, AND A WIER-LIKE SPILLWAY AT ABOUT THE POINT OF COMMUNICATION OF EACH OF SAID CONDUIT MEANS WITH EACH OF SAID OPEN SECTIONS FOR WITHDRAWING LIQUID FROM EACH OF SAID OPEN SECTIONS INTO EACH OF SAID CONDUITS. 